Glassine paper



Patented Oct. 23, 1945 GLASSIN E PAPER Paul H. Cate, New York, N. Y.,assignor to Kelco Company, San Diego, Calif., a corporation oi.

Delaware No Drawing. Application October 21, 1940, Serial No. 362,166

3 Claims.

This invention relates to glassine paper and to the method of making thesame, and the principal object is to provide a glassine paperhaving analg inate incorporated in the softening solution for the purpose ofimparting to the said paper a greatly increased oil resistance, and alsoyielding a transparent film thereon well-suited for use as greaseproofcoatings on glassine and other types of transparent coatings. l

Glassine paper usuallyconsists of thin transparent paper made fromsulfite pulp, by long continued beating and supercalendering. In makingglassine paper a softening solution is usually applied to the paper.said solution consisting of a water solution of glycerine, invert sugar,or other sugars, or mixtures of all three, said solution being appliedto the paper immediately after it comes from the paper screen, or aftermoistening the paper that has been dried in the paper machine but beforeit is given the usual calendering treatment.

I have discovered that the addition of about 1-2% of a light coloredalginate having a 2% Woolwich viscosity of about 20-40 seconds to theabove aqueous softening solution, containing glyceliminates pinholes andimperfections usually present in the paper and gives a smooth surfacethereto.

I will explain the invention to enable others familiar with the art toadopt and use the same,

and will summarize in the claims the essential features of the inventionfor which protection is desired.

Example 1 A softening solution was made up containing 1% of a, lightcolored sodium alginate having a 2% Woolwlch viscosity of 20-40 seconds,5% glycerine, and 94% water; and same was applied to l the paper in thepaper making machine in the usual manner. The finished paper contained0.3% algin. The turpentine oil resistance test showed 200 secondsaverage on the control paper in which no algin was used, and showed 400seconds average on the algin treated paper.

1 Example 2 A softening solution was made up containing approximately3.3% glycerine, 3/5% sugar, and 0.5% alsinate, and same was sprayed ontothe paper while in the paper making machine. -Subsequent turpentinegrease-resistance tests showed that it took an average of 185 secondsfor the turpentine to penetrate the algin-free control paper, while theaverage time necessary for penetration using the algin treated paper was292 seconds.

Any water soluble alginate may be used; but I prefer to use eithersodium or ammonium alginate made in accordance with U. S. Patents1,81i,981, #2,036,922 and #2,036,934, and having Wo'olwich viscositiesin the range of 20-40 seconds on a 2% solution (which is the time for asteel ball 1% inch in diameter to fall 15 cm. through the solution at 20C. The color of the alginate should besuch that it does not materiallydarken the paper to which it is applied. Alginates containingingredients to aid in their solution such as disclosed in U. S. Patent#2,000,807 can also be used; also alginates of the type described in U.S. Patents #2,128,551 and #2,l63,l47 are suitable, as well as alginateshaving Woolwich viscosities below 20 seconds on a 2% solution. Ingeneral however alginates having Woolwich viscosity values below secondsfunction more satisfactorily than those with higher values,

Usually glassine paper is not a, coated paper; that is, it has no waxor' lacquer coating. However my glassine paper may have applied theretoa coating of parai'iin, wax, oil, lacquer paint, resin, alglnate orother iilm or coating. This coating or film, if ofwax and the like,renders the paper resistant to water, emulsions, and water solutions;while if of resin, the second coatingrenclers the paper resistant tofats, oils, emulsions and water. The paraflin may be applied by dippingthe algintreated glasslne paper into a hot solution thereof; and thewaxes may be applied by first dissolving same in a volatile organicsolvent and then spraying, dipping or brushing such solution onto the 40paper. Mastic, copal, benzoin, shellac, colophony,

dammar, sandarac, amm, and other natural resins, as well as thesynthetic resins may also be used for the second coating.

I claim:

1. ulassine paper comprising paper pulp, glycerlne, and substantially0.3% of an alginate homogeneously incorporated therein to render sameoilreslstant and transparent.

l4. Glassine paper comprising paper .pulp, glycerme, and substantially0.3% of an alginate havmg a 2% Woolwicn viscosity of 20-40 secondshomogeneously incorporated therein to render same oil-resistant andtransparent.

3. Glasslne paper comprising paper pulp, ycerlne, sugar,'and asuostantlally .3 percent of an alglnate homogeneously incorporatedtherein to render same oll-l'eslstant and transparent PAUL H. GATE.

